microblaze: Fix missing bracket in printk

The error was introduced by the patch
"microblaze: Fix coding style issues"
(sha1: 6bd55f0b).

Error message:
arch/microblaze/kernel/setup.c: In function 'machine_early_init':
arch/microblaze/kernel/setup.c:177:3: error: 'pr_cont'
  undeclared (first use in this function)
arch/microblaze/kernel/setup.c:177:3: note: each undeclared
  identifier is reported only once for each function it appears in
arch/microblaze/kernel/setup.c:177:10: error: expected ';'
  before string constant
arch/microblaze/kernel/setup.c:177:33: error: expected statement
  before ')' token

Signed-off-by: Michal Simek <michal.simek@xilinx.com>